1. Field of the Invention
The present invention relates to an exposure control device for a video camera, and more specifically, to an exposure control device for a video camera which has two kinds of sensitivity control functions for controlling an iris diaphragm and an automatic gain controller AGC.
2. Description of the Background Art
Recently, there has been proposed an exposure control device for a video camera by which the operating speed of an iris diaphragm can be changed in accordance with a photographing scene (Japanese Patent Application No.1-184951).
When a photographing scene is continuous or when a main subject is located at the central portion of a picture and only a background is moved, an exposure control device for a video camera decreases the operating speed of an iris diaphragm so that an amount of exposure of the main subject is not exceptionally changed.
Incidentally, the iris diaphragm of a conventional video camera has an automatic gain controller (AGC) disposed to in a subsequent stage thereof and an operating speed (gain control speed) of the AGC is fixed.
Therefore, a problem arises in that even if the operating speed of the iris diaphragm is changed in accordance with a photographing scene as in the case of the above exposure control device for a video camera, the change of brightness of a pictorial image finally depends upon the operating speed of the AGC. and the speed at which the brightness of the pictorial image is changed cannot be adjusted even if only the operating speed of the iris diaphragm is changed.